I'm replacing my old subpanel. (It was from Federal Pacific.)

I'm not rewiring my home. And I understand that I'm not required to use AFCI/GFCI breakers.

Is it possible to use AFCI/GFCI breakers with the new panel? I prefer AFCI/GFCI breakers for the safety benefits they provide.

  • What make and model is your new panel? Do you have GFCI receptacles in the appropriate places already? Do you have any shared neutrals or multi-wire branch circuits? (Look for 14/3 or 12/3 cables coming out of the panel in question) – ThreePhaseEel Aug 13 '20 at 1:37
  • It depends how big your subpanel is and how many circuits it must support. It's easy to paint yourself into a corner with too small a panel and wind up unable to equip GFCI/AFCI. – Harper - Reinstate Monica Aug 13 '20 at 2:16
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    @Haozhun -- does pushing TEST on the GFCIs you do have knock out power to the outlets on the opposite sides of the kitchen and bathroom sinks? – ThreePhaseEel Aug 13 '20 at 3:28
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    yes on one side of kitchen sink, no on the other side; yes on one side of bathroom sink, no on the other side That could be old (no GFCI) vs. new (yes GFCI). But could also be load (no GFCI) vs. line (yes GFCI) - i.e., daisy-chained to protect the second one in each chain. – manassehkatz-Moving 2 Codidact Aug 13 '20 at 3:35
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    @manassehkatz, it turns out all but one outlet in my kitchen, bath, garage, laundry room is GFCI protected already. I did not know that. – Haozhun Aug 13 '20 at 3:49

Go ahead with AFCI for the 15/20A circuits

As long as you don't have any shared neutral situations (look out for 14/3 or 12/3 cables entering the panel as you're wiring it), you shouldn't have any trouble putting your new 15A and 20A branch circuits on AFCIs. I would familiarize yourself with the way Square-D does AFCI trip diagnostics at least, though, so that you can understand how to troubleshoot a case where one of your new AFCI's is tripping.

If you do find a shared neutral or Multi-Wire Branch Circuit, you'll need to use a two-pole AFCI for it, though. This will also ensure that both hots wind up on opposite legs of the feed, preventing the neutral from becoming overloaded.

GFCI breakers aren't going to be useful for much, though

Since you have a 3-wire dryer feed and GFCI protection in most of the required places to begin with, you won't need GFCI breakers at all under the 2017 NEC, and will only need one for an air conditioner circuit (if present) under the 2020 NEC. You may wish to use one if that's the easiest way to extend GFCI protection to the basement, though.

  • Can you elaborate on what 14/3 and 12/3 cables indicate? I saw you referring to that in the question comments as well. And It's not clear to me. Also, I'm curious as to the relationship between 3-wire dryer feed and GFCI. – Haozhun Aug 13 '20 at 4:24
  • @Haozhun -- 2020 NEC requires GFCI for dryers, but 3-wire dryer feeds effectively "bootleg" the dryer's ground off of the dryer's neutral, defeating any attempt at providing GFCI protection to the dryer. And a /3 cable means it has 3 insulated wires (black, white, red) in addition to the bare (or green) ground wire – ThreePhaseEel Aug 13 '20 at 4:32
  • Sorry I didn't ask my question clearly: what does /3 have to do with shared neutral? Is that an indicator of MWBC? – Haozhun Aug 13 '20 at 4:40
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    @Haozhun -- yes, /3 cable for a homerun means you have 2 hots and only 1 neutral, so you have a MWBC and thus a shared neutral to go with that MWBC – ThreePhaseEel Aug 13 '20 at 4:41
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    @ThreePhaseEel One thing most of us know, but important to remind others of is the critical importance of having the hots of a MWBC on opposite legs and that the breakers for that circuit are handle tied together. I know you know that 3ph, but can't hurt to remind others. – George Anderson Aug 13 '20 at 12:25

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